candesco: The problem is called Steam Workshop. Both EU4 and CKII are linked to the workshop. And although you can find some mods over at Nexusmods, the majority is posted at workshop and got updated as well. For CKII most mods over at nexus are outdated and won't work with the latest patch (3.0.1.1) . Some more adult mods can be found at loverslab, such as dark world fantasy.
Next to that both games are still actual and got updates on a regular base, as well as dlc's. Both EU4 and CKII have dozens of dlc. The holy fury dlc for ckII for example is the 13th major dlc for ckII. Next to that there are music dlc's, unit dlc's, cosmetic dlc's, e-books. And there are some bundles. CKII is actually heavy integrated into Steam. Same goes for EU4. Probably the waiting is more until there will be a complete edition, just like the first CK.